The acid-catalyzed reaction of an alkyl oxide, for example, ethylene oxide, with a monomer having an active hydrogen atom and a site of unsaturation, such as hydroxyalkyl methacrylate, to form a polyether monomer, for example, a polyethoxylated methacrylate, is know. Such reactions are typically catalyzed by Lewis acids, such as FeCl3. The polyether monomer products formed in such reactions may undesirably polymerize to form a gel. Typically, a phenolic polymerization inhibitor, such as p-methoxy phenol, is used to inhibit the undesired polymerization of the polyether monomer product.
The use of phenolic polymerization inhibitors has not provided a completely satisfactory solution to the problem of undesired polymerization. It is desirable to minimize or eliminate the presence of O2 in the reaction vessel, since the presence of O2 and alkylene oxide in the reactor may create potentially explosive conditions. However, p-methoxy phenol is ineffective as a polymerization inhibitor in the absence of air. This dilemma is typically addressed by conducting the alkoxylation reaction with some oxygen present in an attempt to balance the two competing concerns. Further, p-methoxy phenol contains an active hydrogen atom, and may therefore react with the alkyl oxide under the reaction conditions. In practice it is typically necessary to add a large amount of amount of p-methoxy phenol to offset its undesired consumption during the reaction.